Cheshire Wildlife Trust Heteroptera and Diptera surveys in the Delamere Forest, 2013-2017 by Phil Brighton 32, Wadeson Way, Croft, Warrington WA3 7JS [email protected] on behalf of Cheshire Wildlife Trust Version 1.0 October 2017 Page 1 of 30 Abstract This report provides the results of a series of heteroptera and diptera surveys carried out in the Delamere Forest itself and some of the satellite woodland and bogs. A full list is given of the 460 species recorded and their distribution across the surveyed area. This species list is interpreted in terms of habitat assemblages using the PANTHEON software recently made available by the Biological Records Centre. This showed a strong representation of wet woodland species in the sample. The national assemblages of peatland and decaying wood species were much less well represented but included a higher proportion of rare or scarce species. Of particular note was the find in 3 new locations of the hoverfly Orthonevra intermedia: Delamere remains the only known British location for this species following the original discovery in 2003. The Red Databook cranefly Idioptera linnei was found at Abbots Moss for the first time since 1969, only the second record in the Delamere area since then. Both these species should benefit from the restoration of the Delamere mossland. Introduction In 2003, at an early stage of the Delamere Lost Mosses project Martin Drake was commissioned to carry out an extensive survey of terrestrial invertebrates across the Delamere area1. The bulk of the records from this survey were of beetles (Coleoptera) and true flies (Diptera), but other orders were also covered. The methods used were sweep-netting, pitfall trapping and direct observation on walks in 27 of the very numerous peat basins in the main block of Delamere forest. An additional 4 peat bodies in the surrounding area (Thieves Moss and Leech Mere in SJ5669, Gull Moss in SJ6068, and Sherratt’s Rough in SJ6169) were also surveyed. This report presents results from my own voluntary and amateur surveys of heteroptera and diptera in this area over the past five seasons. The earlier stages of this work have been described in two earlier reports2,3. Comparison of the results with those of Ref 1 gave confidence that these surveys could make a significant additional contribution to knowledge of the Forest’s invertebrate fauna. Further surveys have been carried out in the succeeding two years, covering additional areas and also extending the range of fly families covered. These surveys have not been limited to the peat basins surveyed in Ref 1. The method of sampling based on sweep-netting of vegetation supplemented by direct visual observations (and capture if required for identification) remains as described in Ref 2. For the purposes of presenting the results, the area covered has been divided into eight parts. The following table lists these and the main specific sites within these visited during the surveys: Abbots Moss area Shemmy Moss, South Bog, Whitegate Way East Finney’s Basin, Harthill Moss Hatchmere area Blain’s Moss, Norley Moss, Hatchmere wood North Alvanley Basin, Bainsbridge, Doolittle, Ham Pool Primrosehill Harrow Hill, Tirley Hollow, Urchin’s Kitchen South Blakemere, Hunger Hill, Linmer South-west Black Lake, Great, Midgel, Hockenhull, Little Midgel West Harrison’s, New Pale, Whitemoor Valleys Table 1 towards the end of this report lists the dates of visits and areas visited as well as the number of records obtained. As in the earlier reports, a “record” denotes the presence of a species in a specific 100m square (ie six-figure grid reference) on a specific date. Owing to the size and complexity of the forest, many of the surveys were also explorations with samples being taken along a lengthy itinerary. Where areas of particularly distinctive and productive habitat have been found repeat visits have been made. The maximum number of records in one day was 164, but the number was much lower on other occasions if other activities were being carried out on the day, if it Page 2 of 30 was early or late in the season with fewer species to be found, or if bad weather curtailed proceedings. Further summarising this information according to the months in which records were obtained gives the following overview: Area Mar Apr May Jun Jul Aug Sep Total Abbots Moss area 17 11 63 91 East 61 61 Hatchmere area 31 58 123 118 168 498 North 19 99 12 35 96 17 278 Primrosehill 23 23 South 33 3 96 23 155 South-west 58 155 120 333 West 8 1 129 159 297 Total number of records 23 58 265 294 175 652 269 1736 This table* shows that particular attention has been paid to the CWT reserve comprising Norley Moss and the Hatchmere wood, both because of the easy access but also the different character of the wet woodland there from the rest of the Delamere Forest. “Hatchmere” was also frequently visited by earlier dipterists (see Ref 2) giving the possibility of finding longer-term changes in the fauna, though this aspect is not explored in the current report. The bias to recording in August has not been intentional: indeed May and June are generally regarded as the peak months for diptera diversity. It should be noted that some of the records in this report are yet to be verified by the local recording centres or national recording schemes. Species recorded Tables 2-7 list the species recorded for each of the areas defined above. The grouping of the data largely follows those explained in the two previous reports2,3, except that the calyptrate fly families are now listed separately: this is because the scope of species covered has been increased thanks to the acquisition of recent identification keys for most of these families. The right-hand column in Tables 2-7 indicates species not recorded in the 2003 survey by Martin Drake. Species recorded in 2003 but not in the 2013-17 surveys are not listed. The following table compares the coverage of the two sets of data in terms of species groups. Group Drake (2003) Current Surveys Not recorded by Combined Drake (2003) total Terrestrial heteroptera 9 60 53 62 Craneflies 75 74 28 103 Hoverflies 38 47 17 55 Empidoidea 120 85 23 143 Calyptrates 33 109 90 123 Other diptera 161 85 30 191 Total no. of species 437 460 242 677 * The total number of records is 3 greater than in Table 1 because 3 ad-hoc records from digital photographers were added (1 of Phalacrocera replicata and 2 of Tanyptera atrata). Page 3 of 30 As noted above, the current surveys have produced 1736 records of species by 6-figure grid location and day. The 2003 data are reported in terms of the detection or not of each species at the 31 individual peat basins over the survey period from 2-18 July. On this basis the total number of diptera and heteroptera records was 2,206. Many of the smaller basins fit well within a 100m square. The largest, Linmer North is approximately 300m across, but Ref 1 notes that the core swamp occupied a small part. Thus there is a rough equivalence can be claimed in the numbers of records in the two surveys. There are however numerous differences. The present survey has not been restricted to the close proximity of the peat basins, but has aimed to cover as large a range of habitats as possible including bracken areas, wayside vegetation and wet woodlands in order to explore the overall biodiversity of the site. This may account for the larger numbers of species of heteroptera and calyptrates found in the present surveys. The 2003 report indicates that all the specimens gathered during a fixed period of sweeping at each location were retained and identified, while in the current surveys specimens were selected from the net in order to limit overload during identification. As a result the 2003 survey achieved considerably longer species lists for groups with many smaller species such as the Empidoidea and the Ephydridae (shore-flies). A further difference between the surveys is that the present series were not restricted to a few weeks of the season, so covering species with early and late flight periods. Thus the two surveys can be considered roughly equivalent in coverage though they represent differently biased samples from the invertebrate fauna of the Delamere area. It seems unlikely that the habitat management carried out since 2003 will have greatly changed the range of species present, though of course it should encourage an increase in abundance of the bog specialist species. PANTHEON analysis The species list from the current surveys has been run through the PANTHEON software which became available on the BRC website during 2017. This software is based on a database linking species to their larval and adult food “guilds”, to their characteristic habitats, and to other associated species such as the hosts of parasitic flies. It also flags up species with a conservation designation and for certain special habitats gives a score representing how specific the species is to that habitat. It should be noted however that it currently contains data for only 3047 fly species whereas the total number on the British list is over 7000. Table 8 lists those species from the present surveys which are flagged up in PANTHEON as having a national conservation designation and/or a score reflecting their fidelity to certain special habitats. The PANTHEON data for other species can be viewed on the BRC website. Various statistics can be generated and they combine to give an overall picture of the Delamere environment, as follows.